1) what do you mean by 'Internal-links'? is it 'your site' -> 'another website'? YES

what impact 'internal-link' makes on PR and SERP? GOOGLE SEE A PAGE AS A PAGE FOR ITS PR CALCULATIONS HOWEVER DEGREE OF RELEVENCE AND WEIGHT GIVEN TO INTERNAL LINK IS LOWER THEN EXTERNAL LINK. ITS LIKE YOU THINK YOU ARE A ROCKSTAR, GOOGLE WILL AGREE BUT WILL BE HAPPY IF OTHERS VOTE THAT.

2) what is 'External-links'? is it 'another website' -> 'your website'? YES

what impact 'external-link' gets on PR and SERP? RELEVENT LINKS FROM RELEVENT SITES FOR RELEVENT CONTENT DO BETTER WITH MORE AND MORE NATURALLY GAINED EXTERNAL LINKS. PR IS JUST A GAME NOWADAYS.

3) what do you called when my website links to its own sub-pages? what impact does it make on PR and SERP? (this qustion is vital for me) REPLIED ABOVE

4) which is the way to link to my own sub-pages? is it TEXT -> http://www.example.com/myself.html OR TEXT -> myself.html? ABSOLUTE LINKING IS A CHOICE FROM GOOGLEPLEX BUT NOT A MUST